Conventional boom trucks such as shown in U.S. Pat. Nos. 4,047,618 and 4,986,721, and French patent publication 2362072, typically either have the cab centrally located and the boom mounted above the cab, or have the cab offset on the chassis (at one side of the chassis) with the boom typically below the chassis in a transport position. In the first situation, the operator in the cab has excellent visibility when operating the boom but the boom truck has a high profile so that it is difficult to properly transport either directly over the roadway, or on some other vehicle. In the latter case, the truck can have a low profile so that it is relatively easy to transport, however the operator when operating the boom does not have a perspective that is as worthwhile as when the cab is located in the central portion of the chassis.
According to the present invention a boom truck is provided that has the advantages of both of the different prior art constructions described above. The boom truck according to the present invention, when in an operating position, has the boom above the cab with the cab centrally located for good operator visibility. However when it is desired to transport the truck, the cab is moved to one side of the chassis, and the boom is lowered to a position where at least a portion (or substantially all) of the boom is below the top of the cab, for ease of transport. The operation of the truck according to the invention, providing for effective movement of the cab between operating and ease of transport positions, is much simpler than in other known configurations in which the cab position is movable for various reasons, such as shown in U.S. Pat. Nos. 3,963,132 and 4,630,700.
According to one aspect of the present invention a boom truck is provided comprising the following components: A chassis having a front end and a rear end, first and second sides, a front axle mounting front wheels, and a rear axle mounting rear wheels. A cab having a top, and positioned on the chassis between the chassis front and rear ends. A boom. A support for the boom mounted between the cab and the chassis rear end. The boom pivotally mounted to the support for pivotal movement about a first, substantially horizontal, axis extending in an imaginary line intersecting the chassis sides. The cab movable with respect to the chassis from a first position positioned beneath the boom, to a second position to one side of the boom so that the boom may be positioned next to the cab with at least a portion of the boom below the top of the cab. And, the boom movable from a first position in which the boom is above the cab when the cab is in the cab first position, and a second position in which the boom is next to the cab when the cab is in the cab second position with a least a portion of the boom below the top of the cab.
The boom truck according to the invention typically further comprises linear tracks (preferably substantially parallel to the first axis) mounted on the chassis and cooperable with the cab for providing movement of the cab between the first and second positions thereof. Preferably the cab is mounted between the axles and is centrally located on the chassis when in the first position.
Preferably the support comprises a stand having a first portion mounted to the chassis for pivotal movement about a second axis substantially parallel to the first axis, and a second portion which mounts the boom for movement about the first axis; and the boom truck further comprises at least one actuator operatively connected to the stand for moving the stand about the second axis so that the boom moves between the first and second positions. The stand typically further comprises a third portion which engages the chassis when the boom is in the first position, and which is disengaged from the chassis when the boom is in the second position. The boom truck may further comprise a locking element for locking the stand third portion to the chassis to prevent rotatable movement of the stand about the second axis unless a locking element has been released; for example the stand at the third portion may comprise a support plate, and the locking element may comprise a plurality of bolts (or other screw threaded fasteners) releasably connecting the support plate to the chassis. The stand typically comprises a pair of substantially triangularly shaped plates each having first, second, and third apices comprising the first, second, and third portions of the stand. Typically the first and second axes are substantially directly above the rear axle when the boom is in the first position.
According to another aspect of the present invention a method of utilizing a boom truck such as described above is provided. The method comprises: When it is desired to transport the boom truck over a roadway in a low volume configuration, (a) substantially horizontally moving the cab to a position horizontally displaced from the boom, and (b) lowering the boom so that it is next to the cab with a least a portion of the boom below the top of the cab; and, when it is desired to use the boom truck for lifting or exerting a force on objects, (c) raising the boom so that it is substantially above the top of the cab, and (d) substantially horizontally moving the cab so that the cab is below the boom.
The method as described above may further comprise, when the cab and boom are in the positions to which they have been moved by the practice of (c) and (d), (e) pivoting the boom about the first axis using the at least one linear actuator so that the front end thereof moves vertically to provide a lifting force on objects connected to the boom front end. Procedure (b) may also be practiced by pivoting the support about the second axis using at least one linear actuator connected between the chassis and the support. There may also be, prior to the practice of (e), the procedure (f) of locking the support to the chassis so that the support cannot move about the second axis.
According to another aspect of the present invention a boom truck is provided comprising the following components: A chassis having a front end and a rear end, first and second sides, a front axle mounting front wheels, and a rear axle mounting rear wheels. A boom. A support for the boom mounted on the chassis adjacent the chassis rear end. The boom pivotally mounted to the support for pivotal movement about a first, substantially horizontal, axis extending substantially parallel to the front and rear axles. The support comprising a stand having a first portion mounted to the chassis for pivotal movement about a second axis substantially parallel to the first axis, and a second portion which mounts the boom for movement about the first axis. At least one actuator operatively connected to the stand for moving the stand about the second axis so that the boom moves between operating and ease-of-transport positions. A third portion of the stand which engages the chassis when the boom is in the operating position, and which is disengaged from the chassis when the boom is in the ease-of-transport position. And, a locking element for locking the stand third portion to the chassis to prevent pivotal movement of the stand about the second axis unless the locking element has been released. The details of the components are preferably as described above.
It is the primary object of the present invention to provide a simple yet effective apparatus and method for allowing effective operation of a boom truck, yet also ease of transport thereof. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.